Mammalian 3',4'-dideoxynorlaudanosoline-1-carboxylic acids were synthesized and obtained as optically pure S-(+)- and R-(-)- hydrobromides. Configuration was established by X-ray analysis of the (+)-rotating hydantoin obtained besides the S-(+)- methylester in the fragmentation of the less polar urea in refluxing butanol. Presence of the compounds in phenyketonurics has been established and enantiospecificity will now be determined.